1. Field of the Invention
The present invention relates to an inkjet recording apparatus. Specifically, it relates to an inkjet recording apparatus which includes a mechanism for applying liquid to a recording medium used in inkjet recording, for a purpose which is, for example, to promote the aggregation of pigment when recording is carried out using an ink containing the pigment as a coloring material.
2. Description of the Related Art
Conventionally, in the field of inkjet recording, there is known a method for applying a pretreatment liquid as an application liquid to a recording area in advance using an application roller in order to improve the quality of images to be recorded on a recording medium. In connection with the aforementioned method, Japanese Patent Application Laid-open No. 2002-137383 A has proposed that recording media requiring pretreatment and those not requiring it are transferred using different transfer passages. In Japanese Patent Application Laid-open No. 2002-137383 A, a mark formed at a designated position of the recording medium is detected by a sensor, thereby finding out what type of recording medium is to be used for printing. Subsequently, a switching claw is caused to turn to match the recording medium with a passage, namely, to guide the recording medium to either an application process passage (a passage where the pretreatment liquid is applied) or an application unnecessary passage (a passage where no pretreatment liquid is applied). In other words, the passage to be followed by the recording medium is selected according to the type of recording medium that is to be used for recording.
In Japanese Patent Application Laid-open No. 2000-137383 A, however, either the application process passage (passage with application) or an application unnecessary passage (passage without application) is selected according to the type of recording medium (paper) that is to be used, but as to the operation in a state that the application liquid is insufficient (or runs out), no explanation is given.
Generally known is the following fact. In the recording apparatus that performs inkjet recording on the recording medium to which application liquid has been applied by a roller, a shortage of the application liquid dries out the liquid circulation circuit including the application roller, and increases the friction resistance of the surfaces of the roller. If printing is continued in this state and in the same way as it has been carried out, the surface of the application roller will be worn out by rollers of various types, which are opposite the application roller (i.e. counter rollers), and by the very recording media. In other words, the shortage of application liquid means that the pretreatment liquid (application liquid) functioning as a lubricant is not left between the application roller and the counter roller or recording medium, or if it is, only insufficiently. As a result, the frictional force between the application roller and the counter roller or recording medium will be increased, and wear of the application roller will progress. Use of a roller with its surface being worn out in applying liquid will not produce the image quality that can otherwise be expected.
As mentioned above, in Japanese Patent Application Laid-open No. 2002-137383 A, the most suitable passage for the recording media is selected. The recording operation, however, is performed following the selected passage even in a case where the pretreatment liquid is insufficient. As a result, there is a possibility that wear of the application roller may progress and may harm the image quality.